Raine Creevy is based on Raine Cunningham, the companion who was intended to come after Ace in the then-unproduced Season 27. A feature in DWM 255 gave the character the name Kate Tollinger, but according to an interview with script editor Andrew Cartmel in DWM 433, the character was always going to be named Raine. The character has been renamed Raine Creevy, as Cartmel had since discovered someone of the name Raine Cunningham existed in real life.

The Doctor and Ace previously met Markus Creevy and the then Major Felnikov in Moscow in November 1967. Both Creevy and Felnikov take some time to realise that Ace is the same girl whom they had last seen more than two decades earlier, having not aged a day in the interim. (AUDIO: Thin Ice)